Rotation-symmetry-enforced coupling of spin and angular momentum for p-orbital bosons

TL;DR

This paper proposes a mechanism for spontaneous spin angular-momentum coupling in p-orbital bosons within optical lattices, leading to a superfluid with Dirac excitations and potential topological phases, driven by many-body correlations.

Contribution

It introduces a novel, interaction-driven spin angular-momentum coupling mechanism in bosonic systems, distinct from relativistic origins, with detailed theoretical and numerical analysis.

Findings

Spontaneous spin-orbit coupling arises from many-body correlations.

The superfluid exhibits Dirac excitations and topological features.

The phase is experimentally accessible at low temperatures.

Abstract

Intrinsic spin angular-momentum coupling of an electron has a relativistic quantum origin with the coupling arising from charged-orbits, which does not carry over to charge-neutral atoms. Here we propose a mechanism of spontaneous generation of spin angular-momentum coupling with spinor atomic bosons loaded into $p$-orbital bands of a two-dimensional optical-lattice. This spin angular-momentum coupling originates from many-body correlations and spontaneous symmetry breaking in a superfluid, with the key ingredients attributed to spin-channel quantum fluctuations and an approximate rotation symmetry. The resultant spin angular-momentum intertwined superfluid has Dirac excitations. In presence of a chemical potential difference for adjacent sites, it provides a bosonic analogue of a symmetry-protected-topological insulator. Through a dynamical mean-field calculation, this novel superfluid is found to be a generic low-temperature phase, and it gives way to Mott localization only at strong interactions and even-integer fillings. We show the temperature to reach this order is accessible with present experiments.